Purchased Arduino UNO R3 last week. I completed the installation steps per Arduino website and ran the "Blink" code with the LED attached to pin 13. Following this, I tried using the Adafruit Motor Shield to control a 12V, DC Stepper. The code was taken directly pasted from Ladyada website <<http://www.ladyada.net/make/mshield/use.html>> with minor tweaks, i.e steps and stepper#. But I could not upload the code on to the arduino and the "Serial Port" selection in "Tools" was grayed out. Now when I connect my Arduino via USB, I cannot establish the COM3 virtual port, initially designated for the microcontroller. Furthermore, Arduino "ON" LED does illuminate but I think I am running an infinite loop of the "Blink" code. This is what I have tried so far:

1. Resetting the board manually. No impact.2. Changing USB cables. No impact.3. Verifying the UBS ports function. Yes they do.4. Used Arduino with another pc. Still the same results.5. Reloading and running the installation process of the board. But my pc does not recognize the board anymore and the board just keeps on running the "Blink" code. Also, the device manager does not recognize any UBS connection or the Arduino COM port.

Are there any more variations I can perform that either may help me understand the errors or fix this problem? Also please let me know if you need more information regarding my setup.

The Arduino will always come up running the last code that was burned into flash, so running the blink code just indicates that the 328P microprocessor is still healthy. The problem here is somewhere in the USB/Serial communication link.

When attempting to upload, do you see any change in led activity? (other than the steady blink of the blink code).

There is no change in LED activity upon uploading a code. Well primarily because I cannot establish connection through my COM3 serial port. I've read threads indicating that a pc/usb comm. error may be due to a 8u2 chip on the board requiring firmware update or a reset. Pasted below is the error message from my uploading attempt:

Binary sketch size: 1,084 bytes (of a 32,256 byte maximum)processing.app.SerialNotFoundException: Serial port 'COM3' not found. Did you select the right one from the Tools > Serial Port menu? at processing.app.Serial.<init>(Serial.java:191) at processing.app.Serial.<init>(Serial.java:77) at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:77) at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:172) at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67) at processing.app.Sketch.upload(Sketch.java:1706) at processing.app.Sketch.exportApplet(Sketch.java:1662) at processing.app.Sketch.exportApplet(Sketch.java:1634) at processing.app.Editor$DefaultExportHandler.run(Editor.java:2346) at java.lang.Thread.run(Thread.java:619

Another issue, after establishing successful USB comm. w/ my PC by resetting and reloading a new HEX file to my Atmega 16u2 using Atmel, the Arduino cannot upload a sketch because it says the COM# port is "in use". This issue continues even when I switch between COM ports and/or pc. I disabled my Atmega16u2 driver through my device manager. Any clues why this is happening?